Function: checkSignature()

// Grab the headers that we need to use for verification
const twitchEventSubMessageSignature = request.headers['twitch-eventsub-message-signature'];
const twitchEventSubMessageId = request.headers['twitch-eventsub-message-id'];
const twitchEventSubMessageTimestamp = request.headers['twitch-eventsub-message-timestamp'];

// If there is no body then tell Twitch they are sending malformed data
if (!isObject(request.body)) return response.badRequest('Malformed data received');

// If any of the headers is missing tell Twitch they are sending invalid data
if (!twitchEventSubMessageSignature || !twitchEventSubMessageId || !twitchEventSubMessageTimestamp) {
	return response.badRequest('Missing required Twitch Eventsub headers');
}

// Construct the verification signature
const twitchEventSubMessage = twitchEventSubMessageId + twitchEventSubMessageTimestamp + JSON.stringify(request.body);

// Split the algorithm from the signature
const [algorithm, signature] = twitchEventSubMessageSignature.toString().split('=', 2);

// Verify the signature
if (!twitch.checkSignature(algorithm, signature, twitchEventSubMessage)) {
	return response.forbidden('Invalid Hub signature');
}